SPERM ATOGENESIS OF THE MYRIOPODS. 149 



it i- connected by mantle fibers to only one pole of the spindle. 

 It i> not divided by the first spermatocyte division but passes to 

 one pole entire. Thus the result is in a sense similar to a reduc- 

 tion. il division, the two cells differing as regards the distribution 

 of tin- element. It has no synaptic mate and is, therefore, dis- 

 tributed to only one of the resulting cells (Figs. 19, 20). 



1 1 i- exident tli.it the unequal distribution of the accessory 

 chromosomes produces two sorts of secondary spermatocytes 

 OIK- half li,i\in;^ only the sixteen ordinary chromosomes and one 

 halt" ha\in^ t lie accessory chromosome in addition. By the 

 second -peim.itoi \ te division, the accessory chromosome is di- 

 vided ,nid ,i- it 01 curs in but half of the second spermatocytes it i- 

 distributed to only half of the spermatids, thus giving rise to a 

 dimorphism among the spermatids and spermatozoa. The signi- 

 ficance ot tin- dimorphism has been discussed by a number of 

 investigators McClung 1 (:O2), Wilson 2 (:o6), Stevens 3 (:o8, :o8a, 

 :o<,i Uoring' i 107) and others and, as I have nothing new in the 

 \\.i\ ot ol.MT\ations to offer it would appear hardly profitable to 

 consider the -ul>jeci in detail. I believe, however, that when the 

 i-hromo-ome- o| the female germ cells of Scolopemlra are studied 

 it \\ill be toiind that these are thirty-four in number in the 

 ovogonia, and that the following fertilization formula? of \\'ilson 

 \\ill hold good for this species: 



.V / including \ 



>on I = A ' nuile). 



2 2 \ accessory / 



\ N ( accessory \ 



.-miatozoon - i I 1 = AT - i (male). 



K. t I . :02. "The Accessory Chromosome Sex Determinant?" 

 Hi. .I BULL., Vol. <. ]>p- 43-84. 



\\ ilson, I l< -uidies on Chromosomes III.. The Sexual Differences of 



thr ( hi. .111. -.MIL- i -i. .up in Hemiptcra. with some Considerations on the Deter- 

 inin.Lticin .in.l lnh.-iit.ince of Sex." Journ. Exp. Zoo/., Vol. III., pp. 1-40. 6 fig. 



'Si \ \I., :o8, "A Study of the Germ Cells of Certain Diptera with 



Ri-i.-iciii i- t.> tin- 11- : -.-chromosomes and the Phenomena of Synapsis," Journ. 

 E*i Vol. \'.. pp. 359-374. 4 plates. 



x t ,\, , "The Chromosomes in Diabrotica -.iltala, etc.," Journ. 



\ ..1. \ .. pp. 453-469, 3 plates. 



Stevens, X. M . :OQ, "Further studies on the Chromosomes of Coleoptera." 

 Jur>i. l:.\r,r. /. / . \".-l. \"I., pp. 101-113. 4 plates. 



'BmiiK. Ali.v M.. 107. "A Study of the Spermatogenesis of Twenty-two Species 

 i.t tin- NK inbi.n 1 i , Jassidae. Cercopidse and Fulgoridse." Journ. Kxp. Zoo/., Vol. 

 1\ .. pp. 4'.<>-5i2, 9 plates. 



